Skeletal Muscle

Question 0

What surrounds: muscle; muscle fascicle; muscle fiber?

Answer 0

Epimysium; Perimysium; Endomysium.

Question 1

Control and appearance of Skeletal muscle?

Answer 1

Voluntary control; striated.

Question 2

Muscle fibers contain?

Answer 2

Myofibrils.

Question 3

smallest unit of contraction?

Answer 3

Sarcomere.

Question 4

Skeletal muscles controlled by what neurons?

Answer 4

Somatic motor neurons - voluntary control.

Question 5

Tension: contraction and relaxation?

Answer 5

Shortening and lengthening myofibrils (sarcomeres).

Question 6

5 “areas” of sarcomere?

Answer 6

Z-discs; M-line; H-zone; A-band; I-band.

Question 7

Elastic structure of sarcomere?

Answer 7

Titin

Question 8

Proteins regulating contraction?

Answer 8

Troponin and Tropomyosin.

Question 9

Filaments present in areas?

Answer 9

A-band: thick partially overlapping thin (across M-line and H-zone)
H-zone: only thick
I-band: only thin
Z-disc: thin attached (toward M-line)
M-line: thick attached (toward Z-disc)

Question 10

Area(s) unchanged (constant length) during contraction?

Area(s) shorten during contraction?

Answer 10

A-band.

H-zone & I-band.

Question 11

Stimulus for contraction?

Answer 11

Calcium.

Question 12

Process of crossbridge cycling

Answer 12

1. Myosin bound to actin (rigor state)
2. ATP bind to myosin head - detachment from thin actin filament
3. ATPase activity of myosin hydrolyses ATP. ADP and Pi remain bound.
4. Hydrolysis causes conformational change - head swivel and bind to actin.
5. Release of Pi causes power stroke
6. ADP released - head bound in rigor state to actin

Question 13

What binds to troponin to move tropomyosin from MBS?

Answer 13

Calcium.

Question 14

Triad consists of?

Answer 14

T-Tubule and 2 cisternae.

Question 15

Calcium release from which channels to cause contraction?

Answer 15

Ryanodine receptors (RyRs)

Question 16

Calcium uptake through which ATP dependent structure to cause relaxation?

Answer 16

SERCA pump

Question 17

Calcium is stored in which structure?

Answer 17

Sarcoplasmic Riticulum

Question 18

Membrane resting potential of Skeletal Muscle?

Answer 18

-70mV

Question 19

Distribution of ions across cell membrane?

Answer 19

Na+ outside and K+ inside cell.

Question 20

Depolarisation caused by?

Answer 20

Na+ influx through voltage gated sodium channels.

Question 21

Repolarisation caused by?

Answer 21

K+ efflux through voltage gate Potassium channels.

Question 22

Neurotransmitter that crosses synapse? Receptor that receives it?

Answer 22

Acetylcholine (Ach) and Nicotinic Receptors.

Question 23

Exocytosis of vesicles caused by?

Answer 23

AP and influx of Ca2+.

Question 24

On motor end plate, Na+ and K+ move through which channel?

Answer 24

Nicotinic receptor (opened by binding of Ach).

Question 25

Excitation-Contraction process?

Answer 25

1. Ach released - bind to Nicotinic Receptors 2. AP reach T-tubules - activate membrane protein (DHPR) or (LTCC) which opens RyRs. 3. Ca2+ released from SR 4. Ca2+ bind to troponin, move tropomyosin and expose MBS 5. Myosin bind to actin - contraction occurs 6. SERCA take up Ca2+ into SR 7. MBSs covered by tropomyosin - no crossbridge cycling 8. Contraction ends 9. Relaxation - lengthening of sarcomere

Question 26

How many APs in one twitch?

Answer 26

+/- 5 - 50 (AP: 2msec; twitch: 10-100msec)

Question 27

Tetanus caused by?

Answer 27

Summation (repeated stimulation)

Question 28

Greatest tension at what sarcomere length?

Answer 28

2.0-2.3micrometers (resting length)

Question 29

What is a muscle unit?

Answer 29

1 somatic motor neuron and all myofibers it innervates

Question 30

Most ATP generated when?

Answer 30

Glycolysis coupled with oxidative phosphorylation

Question 31

Skeletal muscle prefer glucose or fatty acids to generate ATP?

Answer 31

Glucose (aerobic and anaerobic)

Question 32

Types of fatigue?

Answer 32

Central fatigue and peripheral fatigue.